Trich is different from Bacterial Vaginosis which used to be known as Gardnerella. You are right about Trich, it is a microorganism and it is sexually transmitted. BV on the other hand, can be acquired even in virginity although it is not common. BV is simply a bacterial imbalance.
Here is a reprinting of some common medical literature on BV found on the internet... this is LENGTHY
What is bacterial vaginosis?
Bacterial vaginosis is a NOT an infection. It is an overgrowth of harmful bacteria in the vagina due to the depletion of very valuable lactobacillus - reason unknown. The vagina normally contains a lot of "good" bacteria, called lactobacilli (say: "lack-toe bah-sil-li"), and a few other types of bacteria, called anaerobes (say: "ann-air-robes"). Too many anaerobes can cause bacterial vaginosis. We don't know why the anaerobe bacteria overgrow and cause this imbalance.
You may notice a discharge from your vagina. The discharge may be clear or colored. It may be very light or heavy. It may have a fishy smell, especially after you have intercourse. Some women have bacterial vaginosis without any symptoms.
Bacterial vaginosis is an overgrowth of bacteria that are normally in the vagina. While it's more common in women who are sexually active, it also occurs in women who are not sexually active. It's not usually necessary for your sex partner to be treated.
Does it have to be treated?
Yes. If the infection isn't treated, the bacteria may get up into the uterus or the fallopian tubes and cause more serious infections. Treating bacterial vaginosis lowers this risk. Treatment is especially important in pregnant women.
How is bacterial vaginosis treated?
It can be treated in one of several ways. Your doctor may prescribe pills for you to take by mouth, or a cream or gel to put in your vagina. It's important to use your medicine exactly as your doctor tells you.
If your doctor prescribes metronidazole (brand name: Flagyl) or other medicines, don't drink any alcohol while taking the medicine or for 24 hours afterward. Combining alcohol with these medicines can cause nausea and vomiting. Even the small amount of alcohol in many cough syrups can cause nausea and vomiting if you're taking metronidazole. Also, be sure to tell your doctor about any other medicines you are currently taking.
Bacterial Vaginosis (BV) is the name of a condition in women where the normal balance of bacteria in the vagina is disrupted and replaced by an overgrowth of certain bacteria. It is sometimes accompanied by discharge, odor, pain, itching, or burning.
Bacterial Vaginosis (BV) is the most common vaginal infection in women of childbearing age. In the United States, as many as 16 percent of pregnant women have BV.
The cause of BV is not fully understood. BV is associated with an imbalance in the bacteria that are normally found in a woman's vagina. The vagina normally contains mostly "good" bacteria, and fewer "harmful" bacteria. BV develops when there is an increase in harmful bacteria.
Not much is known about how women get BV. There are many unanswered questions about the role that harmful bacteria play in causing BV. Any woman can get BV. However, some activities or behaviors can upset the normal balance of bacteria in the vagina and put women at increased risk including:
Having a new sex partner or multiple sex partners,
Using an intrauterine device (IUD) for contraception.
It is not clear what role sexual activity plays in the development of BV. Women do not get BV from toilet seats, bedding, swimming pools, or from touching objects around them. Women that have never had sexual intercourse are rarely affected.
Women with BV may have an abnormal Vaginal Discharge with an unpleasant odor. Some women report a strong fish-like odor, especially after intercourse. Discharge, if present, is usually white or gray; it can be thin. Women with BV may also have burning during urination or itching around the outside of the vagina, or both. Some women with BV report no signs or symptoms at all.
In most cases, BV causes no complications. But there are some serious risks from BV including:
Having BV can increase a woman's susceptibility to HIV infection if she is exposed to the HIV virus.
Having BV increases the chances that an HIV-infected woman can pass HIV to her sex partner.
Having BV has been associated with an increase in the development of pelvic inflammatory disease (PID) following surgical procedures such as a hysterectomy or an abortion.
Having BV while pregnant may put a woman at increased risk for some complications of pregnancy.
BV can increase a woman’s susceptibility to other STDs, such as Chlamydia and gonorrhea.
Pregnant women with BV more often have babies who are born premature or with low birth weight (less than 5 pounds).
The bacteria that cause BV can sometimes infect the uterus (womb) and fallopian tubes (tubes that carry eggs from the ovaries to the uterus). This type of infection is called pelvic inflammatory disease (PID). PID can cause infertility or damage the fallopian tubes enough to increase the future risk of ectopic pregnancy and infertility. Ectopic pregnancy is a life-threatening condition in which a fertilized egg grows outside the uterus, usually in a fallopian tube which can rupture.
A health care provider must examine the vagina for signs of BV and perform laboratory tests on a sample of vaginal fluid to look for bacteria associated with BV.
Although BV will sometimes clear up without treatment, all women with symptoms of BV should be treated to avoid such complications as PID. Male partners generally do not need to be treated. However, BV may spread between female sex partners.
Treatment is especially important for pregnant women. All pregnant women who have ever had a premature delivery or low birth weight baby should be considered for a BV examination, regardless of symptoms, and should be treated if they have BV. All pregnant women who have symptoms of BV should be checked and treated.
Some physicians recommend that all women undergoing a hysterectomy or abortion be treated for BV prior to the procedure, regardless of symptoms, to reduce their risk of developing PID.
BV is treatable with antibiotics prescribed by a health care provider. Two different antibiotics are recommended as treatment for BV: metronidazole or clindamycin. Either can be used with non-pregnant or pregnant women, but the recommended dosages differ. Women with BV who are HIV-positive should receive the same treatment as those who are HIV-negative.
BV can recur after treatment.
BV is not completely understood by scientists, and the best ways to prevent it are unknown. However, it is known that BV is associated with having a new sex partner or having multiple sex partners. It is seldom found in women who have never had intercourse.
The following basic prevention steps can help reduce the risk of upsetting the natural balance of bacteria in the vagina and developing BV:
Limit the number of sex partners.
Do not douche.
Use all of the medicine prescribed for treatment of BV, even if the signs and symptoms go away.
What is Bacterial Vaginosis (BV)?
It is a change in the normal bacteria of the vagina.
What causes BV?
The exact cause of BV is unknown. There are many bacteria that live in a normal vagina. When you have BV, there are not enough “good” bacteria. This causes harmful bacteria to grow in the vagina, causing the vaginal environment to be out of balance.
What are the symptoms?
Most women with BV have no symptoms at all. Sometimes a woman has more Vaginal Discharge than usual. The discharge might be milky with a “fishy” odor. The odor can be worse after sex. Other symptoms women may experience include itching or burning in or near the vagina.
How serious is BV?
BV is usually not serious. In some cases, however, it can cause infections in the uterus and fallopian tubes. It is important to treat BV, especially before having an IUD inserted, an abortion, or tests done on the uterine lining. BV during pregnancy may cause the baby to be born too soon.
How can I find out if I have BV?
The clinician will do a few simple tests in the clinic. Looking at the Vaginal Discharge under the microscope for bacteria and checking the acid level of the vagina are two tests that help the clinician decide if a woman has BV.
How is BV treated?
The clinician can prescribe an antibiotic, taken by mouth, called metronidazole or Flagyl®. There is also a vaginal cream. This medicine can cause nausea or a metal aftertaste in the mouth for some people. Take it with food. DO NOT DRINK ALCOHOL ANY TIME WHILE TAKING THIS MEDICINE. This medicine can cause severe nausea and vomiting when combined with alcohol. Either use a condom or do not have sex until you have finished taking the antibiotic. The clinician can order antibiotic vaginal creams or gels which work just as well, but the cost is higher. The side effects are less with vaginal antibiotics.
What about my partner?
Your partner does not need to be treated because BV has not been proven to be a sexually transmitted infection.
How can I prevent BV?
Some women get BV again and again. It is not clear why or how this happens. These suggestions for good vaginal health may help:
Wipe from front to back (away from the vagina) after bowel movements to avoid spreading bacteria from the rectum to the vagina.
Keep the vulva (outside of the vagina) dry and clean.
DO NOT DOUCHE. Douching is never a good idea, especially with BV.
Avoid feminine hygiene sprays, harsh soaps, or soaps with lots of perfume.
Avoid clothing that can trap moisture: pantyhose (wear pantyhose with cotton crotch) or latex exercise clothing.
Using condoms may decrease BV recurrence for some women.
A healthy vagina normally contains many microorganisms, one of the common ones being Lactobacillus acidophilus. Lactobacillus appears to help prevent other vaginal microorganisms from multiplying to a level where they cause symptoms. The microorganisms involved in BV include Gardnerella vaginalis, Mobiluncus, Bacteroides, and Mycoplasma. For reasons not well understood, the numbers of these organisms increase with BV while the number of lactobacillus organisms decreases.
Most cases of bacterial vaginosis occur in sexually active women between the ages of 15 and 44, especially after contact with a new partner. Condoms do not appear to provide protection, but use of spermicides increases BV risk somewhat. Although BV appears to be associated with and triggered by sexual intercourse, it does not appear to be transmitted from one partner to another. Rather, it is a disordering of the chemical and biological balance of the normal flora. Pregnant women and women with a sexually transmitted disease are especially at risk for getting this infection. Bacterial vaginosis does not usually affect women after menopause.
Untreated bacterial vaginosis can cause pelvic inflammatory disease which can cause fatal complications of pregnancy, premature delivery and low birth weight of infants.